Inhalation devices are known to be used for local administration of drugs to the respiratory tract and lungs of patients. One such device for use with blister packs in which the medicament is held in powder form in the blisters thereof is known as the DISKHALER inhalation device and is described in UK Patent No. 2178965. In use, a fresh blister is indexed to bring it into registration with a use station and then punctured with a puncturing member in two distinct actions to enable the medicament to be inhaled therefrom.
Another inhalation device described in UK Patent No. 2242134 is for use with peelable medicament packs defining containers for holding the medicament and includes a means for peeling the medicament pack apart to open each container in turn as they are brought into registration with a use station. This device is somewhat complex and contains many components.
Medicament for administration by inhalation should be of a controlled particle size in order to achieve maximum penetration in to the lungs, preferably in the range of 1 to 10 micrometers in diameter and more preferably 1 to 5 micrometers. Unfortunately, powders in this particle size range, hereinafter referred to as fine powders, for example micronised powders, usually have very poor flow characteristics due to the cohesive forces between the individual particles which make them readily agglomerate together to form bridges which are not readily broken apart to become free flowing. These characteristics create handling and metering difficulties which adversely affect the accurate dispensing of doses of the powder. However, co-pending PCT Patent Application No. EP96.03274 (filed in the United States as U.S. patent application Ser. No. 09/000093 on Feb. 2, 1998) describes how, by careful sizing of fine agglomerated powder, it is possible to make use of the cohesive forces between the particles to create agglomerates of powder which are free flowing. These agglomerates of powder can be easily handled and may be used to conveniently fill devices.
However, for efficient delivery to the lungs, the powder agglomerates must be broken down before they leave such a device, back into a controlled size.
It has been found that it is possible to break up powder agglomerates in the airflow as a user inhales by incorporating a series of baffles in the mouthpiece of a powder inhalation device. EP 0 237 507 describes baffles which comprise helical channel portions which give the airflow a rotating, helical pattern of motion.
However, one disadvantage associated with the baffles described in EP 0 237 507 in that the baffles comprise a number of components rendering the device manufacturing process relatively complicated and expensive.
GB 2191718 relates to aerosol devices for dispensing nicotine. The nicotine dispensing device has an impaction means designed to separate the spray allowing the smaller particles and vapour phase to flow around the baffle while the larger particles are removed.
PCT/EP93/00582 also describes a device comprising baffles which are acting as separators, but if the aerosol contains larger particles in the form of relatively loose agglomerates, these agglomerates are reduced in size if their velocity of impact against the baffles is sufficiently high.
One disadvantage of the two sets of baffles described in GB 2191718 and PCT/EP93/00582 is the high deposition of powder which can occur due to the baffles extending from the walls of the device at 90.degree. to the direction of airflow. This may result in deposition of the larger agglomerates of powder occurring, which agglomerates could become loose in subsequent inhalations and result in variations in dosage.
It is an object of the invention to provide a device of the type just described which is simple for a user to operate and which is not unduly complex in its assembly. It is a further object to provide a device which may be filled with powder agglomerates but will deliver powder in a form suitable for administration by inhalation.